docs: def strictly_increasing(self):
          """
          :returns:
            a new vulnerability function that is strictly increasing.
            It is built by removing piece of the function where the mean
            loss ratio is constant.
          """
          imls, mlrs, covs = [], [], []
  
          previous_mlr = None
          for i, mlr in enumerate(self.mean_loss_ratios):
              if previous_mlr == mlr:
                  continue
              else:
                  mlrs.append(mlr)
                  imls.append(self.imls[i])
                  covs.append(self.covs[i])
                  previous_mlr = mlr
  
          return self.__class__(
              self.id, self.imt, imls, mlrs, covs, self.distribution_name)